The present invention relates to closed circuit refrigeration systems having a metering device such as an expansion valve, a condenser, a compressor, and an evaporator. More particularly, the invention relates to a sub-cooler for a refrigeration system which cools the liquid and condenses vapor in the liquid line prior to the liquids passing through the metering device.
Refrigeration systems consume a significant portion of all electrical energy generated in the United States. Because the systems have to operate at different ambient temperatures, they seldom operate at the most efficient level. Accordingly, a substantial amount of energy is wasted.
One problem which causes a portion of this inefficiency is the formation of vapor in the liquid refrigerant line between the condenser and the metering device. In many systems, there is a long piece of tubing between the condenser and the metering device. As the liquid refrigerant passes through this tubing it can absorb heat if the ambient temperature is high, causing vapor to form. Additionally, pressure reductions in the line as a result of friction or decreases in the head pressure as the refrigerant moves further from the compressor and condenser can contribute to the formation of vapor. Because the metering devices generally are sized for passing only liquid, any vapor in the line significantly decreases the efficiency of the system by decreasing the amount of liquid which can pass through the metering device to the evaporator.
Various approaches procedures have been developed and utilized to overcome the problem of vapor formation. One approach involves increasing the pressure in the liquid refrigerant line to a point that no vapor will form under most or all operating conditions which the system is likely to encounter. However, this requires a larger compressor than would otherwise be necessary, resulting in a greater use of power to run the compressor.
Another approach is disclosed in U.S. Pat. No. 4,259,848 to Voigt. In this system, vapor formed by exposure of the liquid refrigerant conduit to ambient conditions is withdrawn from a receiver by a dual suction compressor, and the refrigerant approaching the expansion valve is adiabatically cooled in a heat exchanger to liquefy any additional vapor formed by the withdrawal of vaporized refrigerant from the high pressure portion of the circuit. While this system works under some circumstances, it still has several drawbacks. For example, it cannot be used effectively on refrigeration systems utilizing a hot gas defrost. Additionally, a complicated valving mechanism between the receiver and the compressor is required to control the flow of vaporized refrigerant from the high pressure line back to the compressor. Also, the metering device in such a system must be an expansion valve.
Accordingly, it would be a significant advancement in the art to provide a fixed, mechanical condensing sub-cooler which could be used in closed circuit refrigeration systems to cool the liquid refrigerant and to condense vapor formed in the high pressure liquid line before it passes through the metering device. It would be particularly advantageous to provide such a system which is simple in construction and operation, and which is effective. Such a system is disclosed and claimed herein.